An Epidemiology and Biostatistics Core Unit will be established to provide needed technical support and to coordinate the activities related to the conduct of studies in humans. The aims of the unit are fourfold: 1. To organize a centralized facility for the collection, preparation, and storage of human specimens. 2. To adapt for use in human subjects the new bioassays developed in experimental models in the project's components. 3. To design and conduct small scale epidemiologic studies among individuals occupationally or environmentally exposed to chromium or cadmium to help determine whether and how effectively the proposed assays could be employed, together or in a determined sequence and along with traditional exposure assessment methods, to provide comprehensive, quantitive measures of human environmental exposure (biologic dose, susceptibility, and early biologic effects). 4. To provide individual components with biostatistical support in the design and in the analysis of the results of experiments. In the early phases of the project, the expected human specimen requirements of each component will be determined so that protocols for a centralized and standardized collection, preparation, and storage of specimens could be worked out. To adapt the new bioassays for use in human studies, the Unit will be involved in testing the methods of specimen collection in field studies and in characterizing the background variability of the proposed assays in order to quantify measurement error and to propose ways of reducing it. This phase will require accessing volunteer, unexposed human studies in several pilot epidemiologic studies among subjects occupationally and environmentally exposed to the compounds of interest to determine whether and how the proposed biomarkers could be used in full scale epidemiologic investigations. Finally, the Unit will provide comprehensive biostatistical support for the needs of all components and in the analyses of studies in humans.